JP2566868B2 - Multilayer ceramic wiring board including through holes and method of manufacturing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer ceramic wiring board having a structure in which openings at both ends of a through hole are covered with insulating layers provided on both surfaces of the board. More specifically, the openings at both ends of the through-hole have sufficient electrical reliability, and the recesses in the openings of the insulating layer provided on both sides of the substrate are small. The present invention relates to a multilayer ceramic wiring board that can be miniaturized without hindering wiring, has low cost, and is excellent in mass productivity.

[0002]

2. Description of the Related Art In recent years, semiconductor devices have become smaller and higher in performance, and accordingly, a technique for forming a multilayer circuit on a ceramic substrate with a high yield and in a simple manner is required. As a means for increasing the density of a substrate, a multilayer ceramic substrate in which circuits are multilayered by a method called a printing multilayer method or a green sheet multilayer method has been conventionally used. The printing multilayer method is a method of printing an insulating material paste on the surface of a ceramic substrate and firing it to form an insulating layer.The green sheet multilayer method is a method of printing a large number of unfired ceramic sheets on which circuits are printed. It is a method of forming an insulating layer by stacking and firing.

In the above-mentioned printed multi-layer method, a substrate provided with through holes is used to electrically connect the both sides of the substrate to each other. However, since the insulating material paste flows into the through holes during printing, it is necessary to print while avoiding the openings of the through holes, and there is a problem that wiring is restricted. Also,
The conventional green sheet multilayer method has a problem that the reliability of dimensional accuracy is low because a large number of unfired sheets are laminated and fired.

In contrast to such a conventional green sheet multi-layer method, US Pat. No. 4,645,552 proposes a method in which a ceramic substrate which has been fired in advance is used, a green sheet is laminated on the substrate and fired to form an insulating layer. Has been done.
Since this method uses a fired substrate, it has excellent dimensional accuracy of the product, has high strength through the firing process, has good thermal conductivity, and has the advantage that the product can be manufactured at low cost. However, according to the current method, when a substrate having a through hole is used, the following defects are likely to occur in the through hole portion of the substrate. That is, if a green sheet is laminated on the entire surface of the substrate so as to close the openings at both ends of the through hole, the through hole of the substrate is sealed by the green sheet, and the through hole is depressurized during the cooling process during firing. The ceramic sheet in the state is drawn into the opening of the through hole, a dent is formed in this portion, and there is a case in which fine cracks (microcracks) occur in the green sheet in the opening of the through hole. When a crack occurs, the recess of the insulating layer at the opening of the through hole becomes smaller, but when a circuit pattern is printed on the surface of the insulating layer, the conductor paste that forms the circuit pattern flows at the cracked portion, causing a poor electrical connection or short circuit. May occur.

Therefore, in order to prevent the through hole from being in a depressurized state during firing, the green sheet at the opening on one side of the through hole is punched to release the airtight state. However, it is costly to perform the perforating process on the green sheet, and since the circuit wiring cannot be printed on the perforated portion, there is a problem that the circuit configuration is restricted.

An object of the present invention is to provide a circuit board which solves the above-mentioned problems in the conventional multilayer ceramic circuit board. The present inventors have examined the correlation and electrical reliability between the hole diameter of the through hole and the amount of depression of the ceramic insulating layer from the viewpoint of the manufacturing process and electrical reliability,
The present invention has been completed based on the knowledge that a substrate having an insulating layer having a small through-hole opening and having no microcracks can be easily manufactured.

[0007]

According to the present invention, in a multilayer ceramic wiring substrate in which inner layer wirings are interconnected by non-filling through holes, the openings at both ends of the through holes are the bases.
Provided is a multilayer ceramic wiring board which is directly covered by flat insulating layers provided on both sides of the board . In the present specification, the “flat insulating layer” means
Flat enough to allow conductor printing and microcracks
Insulation layer that does not substantially have insulation failure due to
U.

As a preferred embodiment, there is provided a multilayer ceramic wiring board having through holes with a diameter of 0.25 mm or less. In addition, it has an unfilled through hole
The through-hole opening is covered on the ceramic substrate.
The process of laminating ceramic greens,
The product of the green sheet determined by the through hole diameter
Thermocompression bonding to the substrate under layer pressure, and on the substrate
Characterized by including a step of firing the green sheet
The openings at both ends of the through hole are flat on both sides of the board.
Said multi-layer ceramic covered directly by a flat insulating layer
A method for manufacturing a wiring board is provided.

The present invention will be described in detail below. A ceramic substrate having through holes is used in the present invention. Normally, the thickness is 0.1 to 0 on a 0.635 mm thick alumina substrate.
When laminating glass ceramic green sheets of about 2 mm, the hole diameter should be 0.3 mm or less, preferably 0.15 to 0.25.
An alumina substrate with mm through holes is used.
If the diameter of the through hole is larger than 0.3 mm, microcracks are likely to occur in the ceramic insulating layer at the opening of the through hole. Generally, when the hole diameter is 0.15 to 0.25 mm,
The depression of the ceramic layer is also small, and no microcracks are generated. On the other hand, when the diameter of the through hole is smaller than 0.1 mm, the ceramic layer is not dented, but it is difficult to manufacture the alumina substrate and it is also difficult to print the conductor in the through hole portion.

Incidentally, as the thickness of the green sheet increases, microcracks are less likely to occur at the through hole openings. Similarly, the higher the viscosity of the ceramic layer during firing, the smaller the amount of depression in the through hole portion. Therefore, the thickness and composition of the vitreous ceramic green sheet are selected according to the diameter of the through hole of the alumina substrate. Moreover, when the stacking pressure is increased, the amount of depression of the ceramic layer is reduced, and the equilibrium is gradually achieved. Also, the recessed shape has a shape in which the bottom protrudes when the lamination pressure is low, but the bottom has a flat shape when the lamination pressure is high. This is because the green sheet receives shear stress and microcracks occur,
It is considered that this is because air enters and leaves through the cracks during firing and cooling. Therefore, the lamination pressure is selected so that the amount of depression of the ceramic layer is small and no microcracks are generated.

After firing and cooling the green sheet, a conductor pattern is printed on the surface of the ceramic insulating layer formed by the green sheet to form a predetermined circuit.
A resistor, a capacitor and the like are incorporated in the circuit as needed, and the surface of the circuit is covered with overcoat glass. This series of steps is repeated to form a multilayer circuit.

Examples of the present invention will be shown below together with comparative examples. It should be noted that the present embodiment is an example and does not limit the present invention.

Example 1 Alumina substrate (82 mm) having electrodes of 0.2 inch square centered on through holes (hole diameters of 0.2 mmφ and 0.3 mmφ)
× 82 mm, thickness 630 μm), glass-ceramic green sheets (thickness: unfired 120 μm, fired 65 μm: DuPont's trade name 852AT) are laminated on both sides of the above alumina substrate, and the temperature is 75 ° C. Below, 20, 40, 60, 8 respectively
After pressing with a pressure of 0,100 kg / cm ² for 2 minutes, it was fired in the atmosphere for 60 minutes at 850 ° C. for 10 minutes. After that, it was cooled to form a glass ceramic insulating layer on the surface of the alumina substrate. With respect to this substrate, the stacking pressure and the amount of depression of the insulating layer at the opening of the through hole were measured using a stylus type film thickness meter. The results are shown in Table 1 and FIG.
Shown in As shown in Table 1 and FIG. 1, the substrate having a through hole with a hole diameter of 0.3 mmφ has a lamination pressure of 40 kg / cm ²
When it exceeds the value, the depth of the recess in the insulating layer decreases sharply and the bottom of the recess becomes flat, but as the stacking pressure increases, microcracks occur in the recess, and through this there is a through-hole. This is because the suction force due to the reduced pressure is reduced because air flows in and out. Further, in a substrate having a through hole with a hole diameter of 0.2 mmφ, the change in the amount of depression of the insulating layer was small and the microcracks did not occur up to a stacking pressure of 80 kg / cm ² . However, when the stacking pressure exceeded 100 kg / cm ² , microcracks were recognized although the amount of depression was small. Therefore, under the conditions of this embodiment, a substrate having a through hole having a hole diameter of 0.3 mmφ has a lamination pressure of 40 kg / cm ²
For a substrate having through holes with a hole diameter of 0.2 mmφ, a lamination pressure of 80 kg / cm ² or less is suitable.

[0014]

[Table 1]

Example 2 An alumina substrate having through-hole diameters of 0.20 mmφ and 0.24 mmφ,
A multilayer substrate was manufactured according to the same conditions as in Example 1 except that an alumina substrate having no through holes was used and the laminating pressure was 45 kg / cm ² , and a 0.2-inch square surface layer electrode was formed on one side as a counter electrode. . About each through hole diameter
When the interlayer insulation resistance values (DC 100 V: applied for 1 minute) of the 144 samples were measured, all were 10 MΩ or more. In addition, dozens of samples for each through hole diameter
A DC voltage of 25 V was applied between the opposed electrodes under conditions of 5 ° C. and 85% RH for 100, 200, and 500 hours, respectively, and the interlayer insulation resistance value (DC1 kV: applied for 1 minute) after each time was measured. The results are shown in Table 2 and FIG. As is clear from this result, the through hole opening of the multilayer wiring board of this embodiment has almost the same level of interlayer insulation resistance as when the through hole is not provided, and the reliability of electrical connection is high.

[0016]

[Table 2]

Comparative Example Through-hole diameters of 0.5 mmφ, 0.4 mmφ and 0.3 mm
A multilayer substrate was manufactured under the same conditions as in Example 2 using the same green sheet as in Example 2 except for φ, and the interlayer insulation resistance value was measured. For all 0.5 mmφ and 0.4 mmφ samples, a large number of microcracks were observed on the periphery of the concave part of the insulating layer of the via hole by visual observation, and when the conductor paste was printed on the surface, the conductor paste flowed into the microcracks and the interlayer insulation resistance was It was several Ω and could not be used as an insulating substrate. Similarly, about 10% of the 0.3 mmφ sample had an interlayer resistance value of 10 MΩ or less, indicating poor insulation.

[0018]

The multilayer ceramic wiring board of the present invention has no microcracks at the through hole openings of the insulating layer and has high reliability of electrical connection at the through holes.
Further, the circuit wiring on the surface of the insulating layer is hardly restricted by the recessed portion, so that the circuit configuration is easy. Further, the multilayer ceramic wiring board of the present invention is easy to manufacture,
A reliable product can be easily obtained.

[Brief description of drawings]

FIG. 1 is a graph showing a relationship between a stacking pressure of a green sheet and an amount of dents (average value after firing) in Example 1 of the present invention.

FIG. 2 is a graph showing a change of an interlayer insulation resistance value with respect to an application time in an example of the present invention.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuo Tetoriya 383 Aikimachi, Matsuto-shi, Ishikawa Nikko Co., Ltd. (56) References JP-A-3-261196 (JP, A) JP-A-3-259596 ( JP, A) JP 60-47495 (JP, A) JP 63-156393 (JP, A) Actual development 62-174373 (JP, U)

Claims (3)

(57) [Claims] 1. A multilayer ceramic wiring board in which inner layer wirings are interconnected by non-filling through holes,
The openings at both ends of the through hole are flat on both sides of the board.
A multilayer ceramic wiring board which is directly covered with an insulating layer . 2. The multilayer ceramic wiring board according to claim 1, wherein the through hole has a hole diameter of 0.25 mm or less. 3. A ceramic having unfilled through holes.
On the board, cover the through hole opening with a ceramic
The process of laminating Mick green rust,
Under the stacking pressure determined by the through hole diameter
The process of thermocompression bonding to the substrate and the green sheet on the substrate
The method according to claim 1, further comprising a step of firing the toast.
Or a method for manufacturing a multilayer ceramic wiring board according to item 2.